The 28-year-old dual citizen, who was born to a British mother and American father, won a silver medal in slopestyle at Sochi in 2014 for Team USA but said he would make the switch for the Beijing Olympics.
"This is definitely going to be my last -- my swansong if you will -- and I just want to do it for my mum," he told Sky Sports News.
GB's Atkin, 18, continues fine form with World Cup silver
"She has been my number one supporter; she learned how to ski when I learned how to ski. She was 40 and I was three and it was this thing that we fell in love with together."
He said he would be in better shape for the Games thanks to Britain's less-demanding qualifying process.
"I compete in multiple disciplines and for the U.S., our qualifying process is right up until the Games. It is rigorous and my body was basically destroyed right up until the last Olympic Games," he added.
Kenworthy, who came out as gay in 2015, said he hoped to be an inspiration to the next generation of LGBTQ athletes with dreams of Olympic glory.
"It's not easy to come out -- it's quite scary -- and I think, because there is a lack of people that have done it, that makes it even more scary," he said.
"There certainly is a stigma that surrounds it and, if you're in a team sport, then there's a fear that you are going to mess up the team dynamic, and that things are going to change or shift, and you don't want to be responsible for that.
"If you're in an individual sport, you're worried about losing endorsement deals or being judged poorly, so all those fears are valid unfortunately.
"But once you do come out and take that leap of faith, people will tell you that it's very liberating, that it's very freeing and usually you perform better."
Atkin continues fine form with World Cup silver
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